A wiring layer determining system is known (see Japanese Laid-open Patent Publication No. 2008-129761, for example) which includes a storage device which stores storing parameters for calculating a permissible loss, a loss due to a through hole stab adapted for wiring layers, a loss due to a wiring length; and a processing device which reads the parameter data from the storage device, uses the parameter data to calculate, on a wiring basis and in predetermined order of the wiring layers, the loss due to a through hole stab adapted for wiring layers and the loss due to the wiring length, and determines the respective wiring layers based on the comparison result between the calculated losses and the permissible loss.
According to Japanese Laid-open Patent Publication No. 2008-129761, the wiring layer is determined such that removal of a conductor of the stab by a back drilling is not necessary; however, since a degree of flexibility of a wiring design may be increased if the removal of a conductor of the stab is applied, it is useful for engineering designers to grasp, at a design developing stage, whether the removal of a conductor of the stab can be applied.